A new view on the ISM of galaxies: far-infrared and submillimetre spectroscopy with Herschel

The FIR/submm window is amongst the least explored spectral regions of the electromagnetic spectrum. It is, however, a key to study the general properties of the interstellar medium of galaxies, as it contains important spectral line diagnostics from the neutral, ionized and molecular ISM. The Herschel Space Observatory, successfully launched on 14 May 2009, is the first observatory to cover the entire FIR/submm range between 57 and 672 mum. We discuss the main results from the ISO era on FIR spectroscopy of galaxies and the enormous science potential of the Herschel mission through a presentation of its spectroscopic extragalactic key programs.

💡 Research Summary

The paper presents a comprehensive overview of far‑infrared (FIR) and sub‑millimetre spectroscopy as a pivotal tool for probing the interstellar medium (ISM) of galaxies, and it places the Herschel Space Observatory at the centre of this scientific revolution. The authors begin by emphasizing that the spectral window between 57 µm and 672 µm, although historically under‑explored, contains the most powerful diagnostic lines for neutral, ionised, and molecular gas phases. Key FIR lines such as